1. Field of the Invention
The present invention relates to semiconductor devices and methods for manufacturing the same, and more particularly, to semiconductor devices formed using selective epitaxial silicon growth and methods for manufacturing the same.
2. Description of the Related Art
As the density of semiconductor devices has significantly increased, the design rule has also been reduced, resulting in a decrease in size of semiconductor devices. As a result, many problems occur when devices such as transistors are formed. For example, gates have to have a minimal acceptable length in negative-channel metal oxide semiconductor (NMOS) transistors of a cell area, and in positive-channel metal oxide semiconductor (PMOS) transistors and NMOS transistors of a peripheral area such that the NMOS and PMOS transistors can secure proper device characteristics. However, with the scaling of semiconductor devices, the NMOS and PMOS transistors cannot properly perform their functions due to a short circuit between junctions in a bulk region.
In order to solve these problems, methods of increasing actual gate lengths of transistors have been studied, such as the formation of shallow source/drain junctions.
However, even with the shallow source/drain junctions, because semiconductor devices need to be more scaled, the design rule is likewise reduced. For these reasons, because the distances between source regions and drain regions become reduced to less than the critical value, if a process of forming junctions inevitably accompanies a thermal diffusion process, impurity ions laterally diffuse, thus extending junction areas. Accordingly, in the prior art, because the distances between source and drain regions become too short, source and drain junctions can come in contact with each other, causing a short circuit between source/drain junctions in a bulk region.